Patent GB-450607-A (GB)
Title: Improvements in or relating to metal broaching machines
IPC: B23Q5/06
Filed: 1935-01-28
Abstract: 450,607. Broaching-machines. KING, T. ST. P. C., c/o Lapointe Machine Tool Co., Ltd., Edgware, Middlesex. Jan. 28, 1935, No. 2815. [Class 83 (iii)] A vertical hydraulic broaching-machine has separate hydraulic cylinders controlled by different valves for effecting the working and return strokes, the valve controlling the main operating cylinder being automatically reversed by reversal of the flow from the pump which supplies fluid to said cylinder. The broaching slide 2 is drawn downwards' on the operative stroke by the ram 4 of a cylinder 1 and the broach is returned to an inoperative position by a lifting cylinder 3. The main cylinder 1 is connected to a reversible variable-delivery pump 6 through a control valve 9 having a central sliding portion provided with piston elements 11, 12, 13. Passages 15, 16 of the valve are connected to the upper and lower ends respectively of the cylinder 1. Return pipes 21, 22 join a pipe 23 leading to the reservoir 8, the pipe 21 including a relief valve 24 constructed as described in Specification 447,300, [Group XXIX]. A check valve 80 permits flow from the reservoir through port 25 and pipe 27 to supply the pump on the return stroke of ram. A connection 32 from the reservoir supplies an auxiliary pump 7 which delivers to a valve 35 controlling the cylinder 3, the movable valve portion being connected through linkage 39, 40 to a pedal 41. A pipe 50 connects this valve to the reservoir and has a branch 51 with a check valve 52 to permit flow from the reservoir to the bottom of cylinder 3. The broaching slide 2 carries a pull bushing 56 and the upper end of the broach may be engaged in a pull bushing 57 carried by the broach lift slide 58, the work table (not shown), being located between the two bushings. The broaching slide carries through rod 60 a projection 61 coacting with collars 64 on a sliding rod 62 which is connected by linkage with the control handle 67. The projection 61 also, coacts with a member 68 carried on a lever 69 connected as shown with the rocking lever 39 and pedal 41. The broach lift slide also has a projection 75 coacting with collars on a sliding rod 76 connected with the pedal. To start the operative stroke the operator depresses the pedal to move the parts to the Fig. 1 position wherein the pump 7 delivers through valve 35 to the upper end of the lifting cylinder the piston of which moves downwardly to engage the broach with the pull bushing 56, the pump 6 being in neutral position. The handle 67 is now moved so that pump 6 delivers to the port 25 thus moving the valve downwardly so that oil can flow to the upper end of cylinder 1 for the working stroke. The piston 5 also continues its downward movement, excess oil from the pump 7 being passed through relief valve 79 and through the pump casing to cool the bearings thereof. As the piston 5 reaches its lowest position the projection 75 operates the valve 35 and moves it to a position wherein the discharge from pump 7 flows along line 54 through the pump casing to the reservoir. At the same time the tool is disengaged from the upper pull bushing. At the end of the operation, the return movement of the broaching slide is started by operating the handle 67 to reverse the pump 6 so that the valve 9 is returned to the Fig. 1 position and pressure oil passes along pipes 17 and 18 to both ends of the main cylinder so that discharge from the upper end of cylinder 1 is added to the pump discharge and a quick return movement is obtained. During this movement the part 68 is actuated to move the valve 35 to direct oil to the upper end of cylinder 3 so that the piston 5 rises more quickly than the main ram and the tool is disconnected from the bushing 56 and moves upwards, allowing a fresh work piece to be positioned. At the end of the upward movements the upper abutment 78 is engaged to move the valve 35 to a neutral position ready for a fresh cycle and the rod 62 is also lifted to its initial position. The valve 24 enables a back pressure to be built up while the ram is operated to minimize pulsations.